Treatment of crude petroleum to prevent corrosion



No Drawing.

Patented June 30, 1931 UNITED .srAr s PATENT ac GHKRLE'S n. errr'onn, orLos ANGELES, CALIFORNIA, essienon, BY MESNE ASSIGN- MENTS, 'rocauuon-rnurzrmn TREATING rnoonssns, turn, or .Los ensures, CALIFORNIA, ACORPORATION or CALIFORNIA TREATMENT CRUDE PETROLEUM TO PREVENT CORROSIONltis well known that certain varieties of crude oil, particularly suchas are produced in the Gulf coastal plain, contain material quantitiesof sulfur in such chemical combination or condition that on standing oron heating they give off vapors which are highly corrosive to steel oriron, and particularly to thesteelof which stills, condensers and otherrefineryiequipment are composed.

It is also well known that many of these crudes, and particularly suchas are high in sulfur, are produced from strata containing salt water orsalt, and that such crudes often entrain material quantities of brine,which causes deposits of salt on metallic surfaces when heated to atemperature sufficient to drive off the water. 7

.It has heretofore been believed that these two phenomena were notconnected, and efforts have heretofore been made to remove the sulfurfrom the crude prior to distillation, in order to 'prevent' theaforesaid corrosion, and to settle or wash the salt water from the oilto prevent incrustation.

1 have discovered that these two phenomena are directly connected andthat the corrosion of metal parts which has heretofore been charged tothe sulfur contained in the oil may, at least in many cases, be actuallydue to the breaking down of sodium chlorid :01" other water-solublechlorids contained in the oil,'with the evolution of chlorin which, inthe presence of steam, acts powerfully on ferrous metals and rapidlycauses the destruction of equipment.

'I have further discovered that if substantially all 'of the salt orsalts be removed from the oil prior to distillation this corrosion ofequipment "will not take place, even when hydmgen sulfid is copiouslyevolved from the heated oil. This leads me to believe (though I do notknow it to be true) that minute quantities of chlorin may act as acarrier, forming a ferrous chilorid which, in the'presence of heat, anexcess of steam and an excess of hydrogen sulfid, is first converted toferrous oxid with the regeneration of the chlori-n, the oxidthenreacting with hydrogen sulfi'd to form the sulfid of iron A Applicationfiled May 28, 1928. .Serial No. 281,861.

of which the corrosion deposit appears to mainly consist.

Be that vas it may, I have ascertained that if the salt be removed thecorrosion does not take place, even after long continued operation ofthe apparatus, and, of course, with the removal of the salt,incrustation is also avoided, a double purpose thus being served.

I have further discovered that in many if not most of the cases in whichcorrosion is severe, the salt contained in the oil is'not all in theform of brine, careful analysis show ing that the content of salt ismuch greater than can be dissolved in the quantity of water present inthe oil. In such cases it has proven impossible to separate the salt bysettling or other gravity-difference method, or even by washing the oilwith hot water and settling. in some cases it has been possible, bymeans of long continued washing, to remove as much as eighty percent ofthe orig inal salt content, but this method does not appear to becommercially feasible, first, be cause corrosion is merely reduced andnot eliminated thereby, and second, because the plosi1 of the washingprocess is prohibitively I have further discovered that the reason whywashing and settling do not sufiice to remove all of the salt'is thatthe oil contains salt in microscopic grains, either dry or containingsufiicient water to render them moist but not sufficient to dissolvethem, and that these grains (or perhaps only such of them as are moist)are coated with a skin which is repellant to water, for which reasonthese grains are notsubject to solution in water on the mere agitationof water with the oil.

I have further discovered that these grains may be stripped oftheirskins and the salt thus be rendered amenable to solution in water and toseparation from the oil, in the manner about to be described.

I first build up a layer of finely pulverized mineral matter in anapparatus in which the oil may be forced through the layer, such as afilter press or a closed percolation tower to which pump or air'pressuremay be applied. The mineral matter should be of a finely porous nature,should not be rendered muddy or slimy by wetting with water, and is mosteffective if it presents many rough or sharp surfaces or angles. Iprefer diatomaceous or infusorial earth, calcined if possible, as

and pumping'the magma into the press, or'

by feeding the pulverized mineral in small proportions into the streamof oil entering the press during the progress of the treatment. Themanner in which the cake is built up is no part of my invention, nor doI limit myself to any particular thickness of cake, as this will dependon the fineness of the mineral matter used and on its degree ofporosity. In using diatomaceous earth it is possible to get good 7results with cakes rangin from one-eighth inch to one inch in thickness,though I prefer to keep the thickness between say one-fourth andone-half inch, as this gives sufiicient depth for complete treatmentwithout causing undue back pressure. Vith coarser and less porousmaterials such as fullers eartha much greater depth, up to severalinches or even feet, maybe used to advantage.

I prepare the oil for treatment in the following manner. First, unlessentirely fluid at atmospheric temperature I heat it to a temperature atwhich it is sufficient fluid to pass readily through the cake under areason able pressure, for instance, from 100 to 120 Fahr. Second, if itcontains any large proportion of emulsion, I first submit it to ademulsifying step, which is no part of my present invention and whichmay be conducted in any ordinary or preferred manneri A quantity ofemulsion slightly greater than is permissible in the finished oil may bedisregarded, as the final treatment usually has a slight demulsifyingeffect, though this is quite incidental and not an object of myinvention. Third, if the oil carries too little water to dissolve thesalts which it is known to contain, I introduce into the oil a smallproportion of water (up to say five or six pounds of water per barrel ofoil) in such manner that the water will be reduced to a state of veryfine subdivision and thoroughly disseminated throughout the oil. Thefirst or heating step and the step of adding water may be combined byheating the oil to the desired temperature by injection into it of lowpressure wet steam, which will condense (particularly into a moving bodyor stream of oil) in a very desirable and favorable condition ofsubdivision and dissemination.

While the step of addition of water may be omitted in case the oilalready contains enough water to dissolve the salt, the deter minationof salt is tedious and, as a small excess of water is not detrimental, Ifind it preferable to make the addition of water in almost every case.

The oil being thus prepared I pump or otherwise force it through thelayer of pulverized mineral and obtain as an effluent an oil free fromsalt, but mixed with droplets of strong brine which, 011 standing,readily sep arate from the oil, leaving it dry and saltfree. The oilthus prepared may be stored or distilled with impunity, without dangerto tanks in which it is stored or to apparatus in which it is distilledor in which its vapors are condensed. e

t should be observed that this simple treatment is neither ademulsification nor a filtration process. It is not demulsification, asthe presence of much emulsion in the oil may or may not interfere withthe desalting, and the emulsion may or may not be broken, the twofunctions thus appearing to be entirely independent and disconnected.For this reason it is prudent to demulsify (if demulsification isrequired at all) prior to the desalting treatment just described. It isnot a simple filtration process because, first, there is no accumulationof emulsion or salt on the intake side of the cake, such as would ob-'viously result if the cake acted merely to strain out the salt granules,and second, because if insufficient water he used the entire cake maybecome choked with salt and become completely impenetrable in a shorttime, while if the proportion of water used is sufiicient the cake willremain open and permeable and treatment may be continued al mostindefinitely.

What I believe actually happens is this: the salt granules aresufliciently small to enter the body of the cake of porous material, butin passing through the microscopic channels between the grains of suchmaterial, and through these grains if the material be of the order ofporosity of diatomaceous earth, the salt- ,crystals are retarded andinterrupted and are thus stripped of such skins of water repellantmaterial as may surround the gran ules. At the same time they aresubjected to contact with minute particles of Water (constantly passingthrough all parts of the cake because of the fine dissemination ofthewater throughout the oil) and are thus brought into the condition ofa strong solution or brine. This brine, having a stronger surfaceattraction than the oil for the min eral material of the cake, displacesthe oil from the mineral grains and thus tends to accumulate intodroplets which are carried through the cake by the oil pressure behindthem as soon as they reach a sufiicient size to obstruct the channels inwhich they form.

In brief, the rationale of the process is to entrap the salt particles,hold them in a relatively fixed pO-SiLlOD, subject them to the fortime,but

cient to bring fluidity; adding to and intimately cible impact of waterparticles by which they are brought into solution, and finally eject thesolution in the form of brine droplets of such dimensions as willspontaneously separate from the oil by sedimentation or other gravityeffect.

If the water present in the oil when it enters the cake be materiallyless than the quantity required to bring the salt into solution, apartial or perhaps a complete separation of the salt will take place fora short as this salt remains in the cake the latter will soon be chokedand the flow of liquid through it will cease, The feed of oil may thenbe interrupted and the cake washed free from salt by the passage ofWater through it. This method of operating requires a constant reversalof feed, from oil to water and vice versa, introduces large excessquantities of water when washing through, and in general is not adesirable operating method from a commercial standpoint, though it fallsentirely Within the purview of my invention.

I greatly prefer to carry out my process continuously: firstdemulsifying the oil, it demulsification is necessary, in a separateoperation; then establishing a flow stream of the oil and continuouslyheating it by the injection of such quantity of steam as will introducethe desired proportion of water; passing the heated flow stream throughthe cake of pulverized materal, and finally separating the eiiiuent fromthe cake into an oil portion and a brine portion. This final step may beeither continuous or intermittent as preferred. Conducted in this mannerthe process becomes ahnost entirely continuous, and need be stopped onlyto replace the cake with fresh material when choked with such entirelyforeign matter as slimy clay which may accompany the water produced withthe oil and which may not be entirely removed prior to the applicationof my process.

It will be understood that the results produced in this process followfrom the simultaneous passage through the cake of salt-containing crudeand a quantity of water suifithe salt or salts into solution, and thatthey will not be produced it the oil is passed through the cake prior tothe addition of the water or if the water be added and thereafterremoved (as by settling) prior to filtration. The desalting eflectherein obtained is a joint function of filtration in the presence ofwater and is not the sum of the functions of separate filtration andtreatment with water.

I claim as my invention:

1. A method of rendering crude petroleum containing inorganic saltsnoncorrosive to metals, comprising: separating from said petroleum anyexcess quantity of emulsion; heating said petroleum to a temperature ofdisseminating throughout said petroleuma suflicient quantity of water todissolve the'salt con-v tained therein; passing said petroleum and saidadded water through a layer of finely pulverized porous material, andseparating the efflux from said layer into an oil portion and a brineportion. V 2. A method of rendering crude petroleum containing inorganicsalts noncorrosive to metals, comprising: heating said petroleumsubstantially free from emulsion to a temperature of fluidity; adding toand intimately disseminating throughout said petroleum a sufficientquantity of water to dissolve the salt contained therein; passing saidpetroleum and said added Water through a layer of finely pulverizedporous material, and separating the eiflux from said layer into an oilportion and a brine portion.

3. A method of rendering crude petroleum containing inorganic saltsnoncorrosive to metals, comprising: heating said petroleum to atemperature of fluidity; adding to and intimately disseminatingthroughout said petroleum less than six pounds of water per barrel ofpetroleum, said water being suificient in quantity to dissolve the saltcontained therein; passing said petroleum and said added water through alayer of finely divided porous material, and separating the efliux fromsaid layer into an oil portion and a brine portion by gravitydifference.

4. A method of rendering crude petroleum containing inorganic saltsnoncorrosive to metals, comprising: adding to and intimatelydisseminating throughout said petroleum a quantity of water sufiicientto dissolve the salt contained therein; passing said petroleum and saidadded water through a layer of finely pulverized porous material, andseparating the efliuX from said layer into an oil portion and a brineportion by gravity differonce.

5. A method of rendering crude petroleum containing inorganic saltsnoncorrosive to metals, comprising: passing said petroleum through alayer of finely pulverized porous material for separating said salt fromsaid petroleum and simultaneously passing through said layer water notoriginally contained in said petroleum for removing said salt from saidporous material.

6. A continuous method of rendering crude petroleum containing inorganicsalts noncorrosive to metals, comprising: establishing a flow stream ofsaid petroleum; injecting steam into said petroleum, thereby heatingsaid petroleum to a temperature of fluidity and simultaneously addingwater to said petroleum in quantity suflicient to dis- I solve the saltcontained therein; passing said heated petroleum and said added waterthrough a layer of finely pulverized porous material, and separating theefllux from said layer into an 011 portion and a brine portion.

7. A method substantiallyas set forth in claim 5 in Which'the layer iscomposed of fine- 1 1y divided diatomaceous earth.

8. A method substantially as setforthin claim 6 in which the layer iscomposed of fine- 5 i 7 1y divided dlatoniaoeous earth. In Witness thatI claim the foregoing I have hereunto subscribed my name this 11th dayof May,-192 8. e CHARLES D GIFFORD.

